Process for dyeing polyester fiber



United States Patent rnocnss non DYEING POLYESTER FIBER Harold P.Landerl, Wilmington, DeL, assignor to E. I. du Pont de Nemours andCompany, Wilmington, Del., a corporation of Delaware No Drawing.Application October 26, 1955 Serial No. 543,038

8 Claims. (Cl. 8-55) This invention relates to an improved process fordyeing polyester fibers such as polyethylene-terephthalate or cellulosetriacetate.

The hydrophobic nature of fibers of the above type ordinarily makestheir dyeing a difficult practical problem. Thus, while it has beenobserved that disperse dyes which were originally developed forcellulose acetate have some afiinity for polyester fibers, the latterare much more resistant to dyeing with such dyes than is celluloseacetate. Under normal dyeing conditions almost no disperse color isabsorbed by polyester fiber. At the boil, a few acetate dyes color thefabric somewhat, but penetration is very poor. There are two methodsknown to increase'the penetration of the disperse color into thepolyester fiber: (a) pressure dyeing at elevated temperatures and (b)use of a carrier at or near the boil. A carrier is a chemical assistanthaving limited water solubility, but which aids in absorption andpenetration of the dye into the fabric.

Several carriers are available which aid in dyeing polyester fibers withdisperse colors. Benzoic acid and; salicyclic acid for example have beenused} Ortho-phenylphenol is another carrier which is customarily usedwhere heavy shades of disperse dyes on polyester fibers are desired.However, use of the currently available carriers presents severalproblems since they are all deficient in many desirable characteristics,for instance from the standpoint of cost, toxicity, odor, ease ofremoval from the fabric, ability to promote transfer of colors (dyelevels) or availability. Conventional carriers used heretofore are alsogenerally injurious to the light fastness of the disperse dyesused and,because most of them are liquid under dyeing conditions, they tend tocause spotting of the fabric and blotchiness.

It is accordingly an object of this invention to provide a process fordyeing polyester fibers with disperse dyes in which level, heavy shadesof dye, having good light fastness, can be obtained on the fabricwithout spotting.

By disperse dyes in this application I mean waterinsoluble organiccolors which are applied to the fiber from near-colloidal aqueousdispersion. Such dyes have hitherto been referred to generally asacetate dyes; see The Chemistry of Synthetic Dyes and Pigments, editedby H. A. Lubs (Reinhold Publishing Corp, 1955), pages 167 to 174.

A further object of this invention is to provide a dyeing process of theabove type, using a carrier which is not toxic or malodorous. Otheraccomplishments and advantages of my invention will appear as thedescription proceeds.

Now according to my invention, the above objects are achieved by dyeingpolyester fibers with disperse dyes in aqueous systems at about 100 C.using as carrier dimethyl terephthalate, and with the added conditionthat at least 2 parts of said carrier shall be present, in a state ofsolution, in each 1000 parts of dye bath.

To explain the significance of the last condition, I wish to state thatdimethyl terphthalate is a solid, essentially insoluble in cold water.At higher temperatures,

it may go sparingly into solution, but the rate of dissolution is soslow that even a concentration of 0.2% by weight, in the presence of adisperse dye, cannot be achieved in reasonable time, considering theeconomics of the dyeing process.

But according to my invention, the dimethyl terephthalateis added to thedye bath in a form of fine subdivision, corresponding at least to mesh(U.S. sieve size series). Such a fine state of subdivision can beachieved, for instance, by conventional dry grinding in a ball mill orcolloid mill. Alternatively, an aqueous dispersion of the agent maybe-milled in a suitable apparatus, and then evacuated to dryness, forinstance, by spray drying. In either case, dispersing agents, an: ionic,cationic or non-ionic may be incorporated into the carrier during themilling procedure. prepared, the product is a free flowing white powder,readily soluble in hot water to produce saturated solutions of the orderof 1% concentration by weight.

Under these conditions, I find that the agent goes readily into solutionand will dissolve to the extent of at least 0.2% by weight. Moreover, Ifind said concentration to be essentially the minimum effective forachieving good dyeings upon polyester fiber with disperse dyes. Aqueousbaths in which the quantity of dimethyl terephthalate actually insolution is much below this figure, generally produce poor results.

As for quantities above this limit, such may be used up to and evenexceeding the saturation point.

Since the dyeing is to be carried out essentially at 100 C., an openvessel may be employed. In other details, the dyeing may proceed inconventional manner, and may contain, for instance, dispersing agents,such as long-chain alcohol sulfates, or other anionic, cationic ornon-ionic surface active agents."-

My improved process yields dyeings of deep shades and characterized bygood levelness and excellent light fastness. geneous fiber, my inventionmay be applied successfully to the dyeing of blends, i.e., fabricscomposed of more than one material, for instance polyester fiber and apolyamide fiber. Heretofore, in the dyeing of such blends the dispersecolor would be sorbed preferentially by the polyamide portion of thefabric, since the rate of solution of the disperse dye in the polyamidefiber is considerably greater than its rate of solution in the polyesterfiber. I found, to my surprise, that the use of dimethyl terephthalateeffectively changes the solubility rate of the disperse dye in thepolyester fiber.

Accordingly, with the use of dimethyl-terephthalate as carrier, uniformdyeings of such blends may be ob tained; This can be done, for instance,by first dyeing the blend using dimethyl terephthalate as carrier andthus causing the disperse color to be preferentially absorbed onto thepolyester fiber. Then a second step is carried out which comprisesdyeing with a nylon dye to match the shade of the polyester fiber, butin the absence of dimethyl terephthalate. Alternatively, simultanecusdyeing of the two fibers from a single bath may Example 1 A dye bath isprepared from 0.05 part of Disperse Yellow dye Prototype No. 534, 0.1part of a commercial long-chain-alkyl sulfate mixture 0 ,10 C 0.5 partof dimethyl terephthalate whose particle size is not coarser lfatentedApr. 26, 1960 When thus In addition to being useful for dyeinghomoassists? than 100 mesh, and 200 parts of water. A piece of spunpolyethylene terephthalate parts by weight) is boiled in this dye bathfor 2 hours. The resulting dyeing is bright, level and has excellentlight fastness.

When cellulose triacetate is dyed with the above dye bath under similarconditions, essentially the same results are obtained.

When the above two dyeing procedures are repeated 7 except for using 0.2part of dimethyl terephthalate in stead of 0.5 part (i.e., 1 part ofcarrier per 1000 parts of dye bath instead of 2.5 parts per 1000) thedycing's ob tained are much weaker than those obtained above.

Example 2 A dye bath comprising 0.05 parts of Dispeme Red dye PrototypeNo. 370, 0.1 part of the long-chain-alkyl sulfate mixture mentioned inExample 1, 0.8 part of dimethyl terephthalate milled to a particle sizenot coarser than 100 mesh, and 200 parts of water is used to dye a 5part sample of spun polyethylene terephthalate as in Exarnple l. whichhas excellent fastness to light and washing.

When cellulose triacetate is dyed with the ab ve dye bath, similarresults are obtained.

Example 3 The fabric is dyed a bright, level red shade A dye bathconsisting of 0.05 part of Disperse Yellow Example 4 r A dye bathconsisting of 0.05 part of Disper'se Red dye Prototype No. 370, 0.1 partof the long-chain-alkyl sulfate of Example 1, 0.4 part of dimethylterephthalate (particle size finer than 100 mesh) is prepared and isused to dye a 5 part piece of fabric composed of equal parts by weightof polyethylene terephthalate filament and nylon filament. Thepolyethylene terephthalate is dyed a strong, bright red shade; the nylonportion is only stained a light pink.

When the above procedure is repeated without the dimethyl terephthalate,the nylon is dyed a heavy red shade while the polyester fiber is onlyslightly dyed.

It will be understood that the details of the above examples may bevaried within the skill of those engaged in this art. For instance, inlieu of the dyes named in the above examples, other disperse dyes may beused, for instance azo dyes, such as Prototype No. 242(yellow),

Prototype No. 245-(green shade of yellow), Prototype No. 43-(orange),

Prototype No. 244-(red),

Prototype No. 236-(red);

disazo dyes, such as SRA Golden Yellow XIII(Lubs, page 171), SRA GoldenOrange I--(Lubs, page 171);

azomethine dyes, anthraquinone dyes, or any other of the disperse dyesdiscussed in the above cited Lubs text at pages 167 et seq.

I claim as my invention:

1. A process of dyeing polyester fiber of the group consisting ofpolyethylene-terephthalate and cellulose triacetare, which comprisestreating the same at boiling temperature with an aqueous dispersion of adisperse dye in the presence of a carrier comprising dimethylterephthalate, said dimethyl tereph-thalate being present in saidaqueous treatment bath in quantity not less than 2 parts per 1000 byweight and being dissolved therein to an extent not less than 2 partsper 1000 by weight.

2. The process of preparing a dye bath for hydrophobic polyester fiber,which comprises dispersing a disperse e in water at the boiling point,and adding to the hot 'aqueous dye bath thus produced solid dimethylterephthalate in a state of subdivision sutficiently fine to dissolve insaid dye bath and to produce therein a concentration not less than 0.2%by weight.

3. The process of preparing a dye bath for hydrophobic polyester fiber,which comprises dispersing a disperse dye in water at the boiling point,and adding to the hot aqueous dye bath thus produced solid dimethylterephthalate in a state of subdivision not coarser than mesh sieve, andin quantity sufficient to form a solution in said dye bath of aconcentration not less than 0.2% by weight.

4. A process as in claim 1, wherein the fiber dyed is polyethyleneterephthalate.

5. A process as in claim 1, wherein the fiber dyed is cellulosetriacetate.

6. A process as in claim 1, wherein the fiber dyed is a blend ofpolyethylene terephthalate and polyamide fibers.

7. A process as in claim 1, wherein the fiber consists at least in partof polyethylene terephthalate.

8. A process of dyeing hydrophobic polyester fiber, which comprisestreating the same at boiling temperature with an aqueous dispersion of adisperse dye in the presence of a carrier comprising dimethylterephthalate, said dimethyl terephthalate being present in said aqueoustreatment bath in quantity not less than 2 parts per 1000 by weight andbeing dissolved therein to an extent not less than 2 parts per 1000 byweight.

References Cited in the file of this patent UNITED STATES PATENTS2,188,160 Rooney Ian. 23, 1940 FOREIGN PATENTS 592,858 Great BritainOct. 1, 1947 595,344 Great Britain Dec. 2, 1947 741,457 Germany Aug. 8,1944 OTHER REFERENCES Zimmerman: Am. Deest. Rep., Apr. 25, 1955, pp.296-302, esp. p. 298.

Tech. Bull. by Du Pont, vol. 8, No. 2, June 1952, pp. 69-76.

Iour. Soc. Dyers and Col. for January 1950, p. 27. Br. Rayon and SilkJour. for July 1951, pp. 58, 59.

1. A PROCESS OF DYEING POLYESTER FIBER OF THE GROUP CONSISTING OFPOLYETHYLENE-TEREPHTHALATE AND CELLULOSE TRIACETATE, WHICH COMPRISESTREATING THE SAME AT BOILING TEMPERATURE WITH AN AQUEOUS DISPERSION OF ADISPERSE DYE IN THE PRESENCE OF A CARRIER COMPRISING DIMETHYLTEREPHTHALATE, SAID DIMETHYL TEREPHTHALATE BEING PRESENT IN SAID AQUEOUSTREATMENT BATH IN QUANTITY NOT LESS THAN 2 PARTS PER 1000 BY WEIGHT ANDBEING DISSOLVED THEREIN TO AN EXTENT NOT LESS THAN 2 PARTS PER 1000 BYWEIGHT.